EyeWorld Asia-Pacific March 2017 Issue

3 EWAP March 2017 Letter from the Editor Dear Friends P erfect IOL prediction is the dream of every eye surgeon and the theme for our current issue of EyeWorld Asia- Pacific . The goal remains elusive but has become increasingly important as complications in cataract surgery have become infrequent and patients’ expectations include freedom from spectacles following surgery. The field of biometry began in the 1880s with the development of the first practical keratometer by Emile Javal. This enabled accurate measurements of the anterior corneal surface and assisted Gullstrand and Tschernig to describe the optics of the human eye. Keratometry together with refraction is sufficient to predict the required intraocular lens power by vergence formulae for an aphakic eye which was the expected state following cataract surgery until Ridley changed the world with the first intraocular lens implantation in 1949. The postop refraction after Ridley’s first IOL implantation was –24.00/6.00 x 30° as the higher index of refraction of polymethylmethacrylate had not been fully accounted for in designing the first intraocular lens. There was no reliable method of measuring axial length in the following decades and the first IOL formula was simply a standard IOL power of ~19.5 D multiplied by the patient’s refraction. Reliable ultrasound machines able to measure axial length became available in the 1970s due to the efforts of pioneers like Karl Ossoinig and Jackson Coleman. Although immersion ultrasound measurements are more reliable, contact A Scan measurements are more easily obtained and became predominant. Inadvertent compression of the cornea was problematic and the prediction accuracy improved dramatically with the introduction of partial coherence interferometry developed by Adolf Fercher with the first IOLMaster in 2000. Errors in axial length measurements were no longer responsible for the majority of unexpected errors and prediction of the effective lens position (ELP) became the limiting factor in most circumstances. Improved formulae became available and modern formulae use additional parameters such as lens thickness available with optical biometers based on optical low coherence reflectometry. More recently, swept-source OCT technology has been introduced. This will allow us to measure the posterior cornea more accurately, which should be most helpful in post-LASIK patients requiring cataract surgery as well as toric calculations. Even spherical equivalent prediction can be enhanced with this technology once fully implemented and integrated with modern formulae. In this issue, experts provide their own perspective and suggestions to enhance IOL power prediction and I hope this brief history of modern biometry provides a useful perspective in how much has been achieved as we strive for perfect IOL prediction. Warmest regards Graham Barrett Chief Medical Editorial EyeWorld Asia-Pacific EYEWORLD ASIA-PACIFIC EDITORIAL BOARD C HIEF MEDICAL EDITOR Graham BARRETT, Australia MEMBERS Abhay VASAVADA, India CHAN Wing Kwong, Singapore CHEE Soon Phaik, Singapore Hiroko BISSEN-MIYAJIMA, Japan Hungwon TCHAH, Korea ASIA-PACIFIC China EDITION Regional Managing Editor YAO Ke Deputy Regional Editors HE Shouzhi ZHAO Jialiang Assistant Editors ShenTu Xing-chao ZHOU Qi ASIA-PACIFIC INDIA EDITION Regional Managing Editor S. NATARAJAN Deputy Regional Editor Abhay VASAVADA ASIA-PACIFIC KOREA EDITION Regional Managing Editor Hungwon TCHAH Deputy Regional Editor Chul Young CHOI John CHANG, Hong Kong Johan HUTAURUK, Indonesia Kimiya SHIMIZU, Japan Pannet Pangputhipong, Thailand Ronald YEOH, Singapore S. NATARAJAN, India Sri GANESH, India YAO Ke, China Y.C. LEE, Malaysia